Mechanisms of stress control in SiNx membranes under gas cluster ion beam irradiation

Ar and O2 gas cluster ion beam (GCIB) irradiations were performed on freestanding SiNx membranes to elucidate the mechanisms governing stress modification. The relationship between irradiation dose, membrane deformation, and oxide layer thickness was examined using white-light interferometry and x-ray photoelectron spectroscopy. O2-GCIB was found to promote oxidation more efficiently than Ar-GCIB, leading to a pronounced relaxation of intrinsic tensile stress. A distinct trend between membrane curvature and oxide thickness at doses below 1.0 × 1013 clusters cm−2 indicates that surface oxidation is the dominant factor governing compressive stress. On the other hand, stress modification under Ar-GCIB irradiation is mainly attributed to defect formation and Ar incorporation. These results highlight that O2-GCIB enables more efficient stress modification through oxidation enhanced by high-energy-density impacts inherent to GCIB, offering a practical route for precise stress control.